Fixed posts Content API test run in isolation

closes https://github.com/TryGhost/Arch/issues/76

- The posts test suite was failing when run in isolation. This was due to "collections" labs flag not being turned on, the events were not going through to collections service correctly

ghost/core/test/e2e-api/content/posts.test.js

@@ -26,6 +26,8 @@ describe('Posts Content API', function () {
     let agent;
 
     before(async function () {
+        // NOTE: can be removed after collections -> GA
+        mockManager.mockLabsEnabled('collections');
         agent = await agentProvider.getContentAPIAgent();
         await fixtureManager.init('owner:post', 'users', 'user:inactive', 'posts', 'tags:extra', 'api_keys', 'newsletters', 'members:newsletters');
         await agent.authenticate();